In order to discuss the prior art, it is necessary to discuss the terminology of foot movement. The human foot is capable of a wide range of motion provided by the ankle joint and the lower leg. The primary motion provided by the ankle joint is dorsal and plantar flexion. In plantar flexion, the foot is pivoted about the ankle joint to move the toes downward below the ankle. This is colloquially known as standing on ones toes. In dorsiflexion, the foot is pivoted about the ankle joint to draw the toes upward above the heel.
The ankle joint also permits limited motion in inversion and eversion. In inversion, the soles of both feet would move toward each other if both feet are inverted simultaneously. In eversion, the soles of the feet would move away from each other if both feet were everted simultaneously.
Finally, the foot and ankle joint may be rotated about an axis extending through the ankle joint and heel by the action of the tibia and fibula, the bones forming the lower leg.
Perhaps the best known prior art apparatus relating to the present invention is the so-called BAPS board. A BAPS board amounts to a board, or elongated surface, which is used in conjunction with a cylindrical support which is hemispherical (in cross-section). The patient places the board on the hemispherical support, the flat side of the support, sitting on the floor or ground. The board then is manipulated with the patient's foot and lower leg in a backward and forward or transverse motion. This exercise tends to strengthen the ankle as well as the calf muscles and those working in opposition thereto. Whether the patient is sitting or standing, use of the BAPS board primarily exercises just the calf and muscles in dorsal and plantar flexion. Moreover, the BAPS board is relatively unstable, potentially subjecting the patient to injury.
U.S. Pat. No. 735,319 to Urwick discloses an exercising apparatus which is an improvement on the BAPS board in that a resistance means (i.e. springs) is employed to resist forward movement of the toes or downward movement of the heel.
U.S. Pat. No. 4,279,415 to Sam Katz discloses an exercise device wherein a platform pivots about an axis adjacent the patient's heel. Cushioned resistance is provided as the foot is pressed against a resilient material between the platform and a supporting platform.
U.S. Pat. No. 4,206,558 to Vincent J. Bivona amounts to an integration of the BAPS board concept. Bivona merges the board with the support to provide a foot surface which is supported by a hyperbolic bottom surface.
U.S. Pat. No. 4,573,678 to Steve Lamb et al. discloses an adjustable footgear that is strapped to the user's foot. The footgear has a base with an angularly adjustable sole platform connected by a heel pivot to a base. The platform has a manual adjustment mechanism for raising the toe end of the platform any select degree above the heel end to dorsiflex the foot upon walking.
U.S. Pat. No. 4,759,542 to Donald P. Hudec discloses a device and method intended to correlate the reflexes of the person using the device. The device is another variation on the BAPS board.
All the aforementioned disclosures relate to lower leg or ankle exercise devices which provide exercise motion substantially in one dimension, namely, the forward and backward dimension in which one foot is flexed. In the terminology discussed above, dorsal and plantar flexion.
U.S. Pat. No. 4,739,986 (Edward J. Kucharik et al.), U.S. Pat. No. 4,452,447 (Lepley et al.), U.S. Pat. No. 4,310,155 (Wilson F. White), U.S. Pat. No. 4,635,932 (James A. Dewces), U.S. Pat. No. 4,251,068 (Edward J. Tarnacki), and U.S. Pat. No. 4,629,181 (Krieve) disclose foot or lower extremity exercisers which provide exercise resistance in two or three dimensions.
U.S. Pat. No. 4,452,447 to Chelsea Lepley et al. describes an ankle exerciser which permits isokinitic exercise of the ankle joint. The device of Lepley et al. separately, and individually, controls the resistance provided against ankle movement about each of the independently controllable, resistive axes.
U.S. Pat. No. 4,739,986 also describes an exercise apparatus which permits three-dimensional exercise of the feet, ankles and lower legs. The device of Kucharik is a spring-mounted assembly wherein the axis of the mount is substantially co-linear with the exerciser's leg.
U.S. Pat. No. 4,629,181 discloses a multi-directional movement leg exerciser comprising a base, a turntable rotatably mounted thereon, and foot supports. The device of the '181 patent provides exercise primarily about a single axis substantially colinear with the exerciser's leg.
None of the above references, disclose or suggest the multi-dimensional, easily portable, yet relatively inexpensive lower extremity exercise apparatus of this invention.